Preparation Of Bioflocculant Using Municipal Sludge And Livestock Wastewater As Substrate

This research aims to prepare two kinds of flocculants with municipal sludge andlivestock wastewater,one is the bioflcculant, the other is the sludge flocculant (SF).When culture pH was7.0, inoculum size was2%(v/v), Na2HPO4concentration was0.5g/L, and the ratio of sludge/livestock wastewater was7:1(v/v), a maximumflocculating rate of87.6%could be achieved. Among13different kinds ofpretreatments for sludge, the optimal one was the thermal-alkaline pretreatment.Approximately1.6g/L crude bioflocculant could be harvested using cold ethanol forextraction. This bioflocculant showed color removal rates up to80%when applied todirect and disperse dye solutions, but only23.0%for reactive dye solutions. Infraredspectrum showed the bioflocculant contained functional groups such as-OH,-NH2and-CONH2. Components in the bioflocculant consisted of91.2%of polysaccharides,7.6%of proteins and1.2%of DNA. When the bioflocculant and copper sulfate(CuSO4) were used together for decolorization in actual dye wastewater, the optimumdecolorization conditions were specified by the response surface methodology (RSM)as pH11, bioflocculant dosage40mg/L and CuSO480mg/L, under which adecolorization rate of93.9%could be reached.When prepare sludge flocculant directly with municipal sludge, differenttreatments of dewatered sludge such as, thermal treatment, acid treatment, alkalinetreatment, ultrasonic treatment, and the combination of them were studied.Flocculating activity of sludge flocculant prepared with thermal treatment was up to99.0%. Active ingredients were in the phase of sludge particles instead of thesupernatants, and mainly were polysaccharide. More than90%flocculating activitycould be reached at pH2.0-12.0. When applied in stimulated wastewater of directdyes, disperse dyes and reactive dyes, the decolorization rate was83.2%,68.8%, and30.2%, respectively. When SF and polyaluminum chloride (PAC) were used in actualdye wastewater, after optimization by response surface methodology, the optimalconditions for decolorization are pH7.0, SF30mg/L and PAC25mg/L, and95%decolorization rate could be achieved. The optimal conditions for COD removal arepH11.0, SF21mg/L and PAC47mg/L, then96.5%COD removal rate was obtained.Compared with high cost traditional method of bioflocculant preparation withstandard fermentation medium, the method in this paper could not only producebioflucculant with municipal sludge and livestock wastewater as cheap medium, but also make the sludge particles into sludge flocculant. Hence, both the supernatant andthe sediments of fermentation broth in this research possess high flocculatingproperties, which could adapt to a wide pH range.